Preliminary evidence attests to the effectiveness of mindfulnessbased interventions in reducing symptoms associated with a variety of medical and psychological conditions. However, research progress has been hampered by discrepancies in how mindfulness has been operationalized, assessed, and practiced. Existing contemporary assessments of mindfulness were developed exclusively by Western scientists and have exhibited questionable validity, particularly among diverse cultural groups. Operational definitions of mindfulness are essential for the development of valid measures, which in turn are necessary for investigating the mechanisms of change in mindfulnessbased interventions. Therefore, the overall goal of this study is to create a mindfulness measure that is informed by the experience of mindfulness experts - Theravada, Tibetan, and Zen Buddhist clergy and lay practitioners. To do so, this study will employ the preliminary phases of the sequential exploratory mixed methods for instrument design model. The first phase will involve conducting openended interviews with Theravada, Tibetan, and Zen Buddhist clergy and lay practitioners to ascertain expert information on mindfulness and closely related Buddhist concepts. This qualitative process allows the experts to define the phenomena of interest (i.e., addresses issues of validity). In the second phase, we will use the themes and specific phrases evoked during the qualitative interviews to develop items for a draft closed ended selfreport measure of mindfulness. Following completion of the research outlined in this proposal, we will submit a subsequent proposal to thoroughly evaluate the psychometric properties of our draft mindfulness questionnaire in a variety of different cultures and contexts. This measure can be beneficial in clinical research by helping to elucidate the mechanisms of change in mindfulnessbased psychotherapies in the United States and equally so in other cultures such as Thailand, where mindfulness and other Buddhist practices have already been integrated into mainstream mental health treatment. Therefore, our aim is to create a measure that can help improve the assessment and clinical use of mindfulness. PUBLIC HEALTH RELEVANCE: Psychological treatments that utilize Eastern-derived techniques such as mindfulness show a great deal of promise in alleviating symptoms associated with depression, anxiety, and related disorders. There is, however, a need to clarify exactly what mindfulness is and how it can best be assessed and integrated into treatment. By relying on the expertise of Theravada, Tibetan, and Zen Buddhist clergy and lay practitioners, the results of this study will enhance the assessment and practice of mindfulness, and therefore help to increase the effectiveness of mindfulness-based psychotherapies.